This is the bane of MVER testing, Mr. Higgens nightmare. How come we had low MVER but the floor failed catastrophically in 6 months?

Wet slabs are dangerous. Let's just agree on that. If the slab is very wet, it has high potential (Copyright JD 2005) for failure. The cement is still hydrating above 85%. Moisture is moving and taking alkaline constituents with it as it moves. We have always known wet slabs are bad news.

Back in the day the only test for slab wetness was placing a desiccant on the slab and covering the desiccant with a vapor tight dome, and then dancing a vapor dance, giving homage to the concrete gods and boozing up the GC to make him your best buddy in case the whole shebang blew up.

You looked at the desiccant after a couple days and it told you NOTHING about the slab besides a tiny bit of information that at this brief instant in time between your brother's third wedding and the birth of the two headed goat at the county fair, the moisture that came out of the slab while the temperature and humidity were just so, was ....X.... an unknown number... Really an insignificant number. You never knew the potential (copyright JD 2005) of the slab... How much water was trapped inside, boiling and seething and jonesing to get out and bring its alkaline posse with it...

And floors failed. Floors failed over bad readings, that we could understand, but hey, floors were failing over good MVER readings.... WHY?

Well we know why, because there is moisture in the concrete that is dying to get out, or at least equilibrate, and that raises havoc with our flooring. So a couple of smart guys figured out that we should and could read the moisture held inside the concrete, and get an idea of the potential (copyright JD 2005) the slab has to experience problems later in life... A slab with a LOT of moisture inside is far more likely to have a failure due to moisture and alkalinity. Even if the slab has a cap that limits MVER such as a sealer, burned surface or it was just read during a high RH period of time in the building.

So, getting off my lectern, yes a hard troweled surface will inhibit MVER, but MVER is a LOUSY indicator of a slab's readiness for flooring... Love ya Bob!

Quote:EC, you sound like a pretty smart fella...
Consider this:
You take an MVER using F1869 on your burned-black, hard surface, compacted concrete. You get a reading of 5lbs. Now to increase your primer bond to the concrete you blast the surface with your handy-dandy blaster machine.

So now if the surface structure was inhibiting dry out and is only reading 5lbs isin't this escentually a good thing? And the moisture in the concrete is thus equilibrated already because of this burned-black, hard surface, compacted concrete?

Someone is not making logical sense here. Me thinks you had to many peyote buttons doing your dance around the fire.

Yes, low MVER is a good thing, if it is accompanied by low RH. High RH and low MVER does not make a slab safe for moisture sensitive flooring. There is still a lot of moisture gurgling in there moving alkalinity and also moving water as the slab equilibrates over time.

This key point is where the revolution is taking place. The old MVER tests have failed us, floors were blowing up and nobody understood why. Now we know, low MVER is almost completely irrelevant for indicating an acceptable floor.

You can read that again, low MVER is almost irrelevant for indicating readiness for flooring.

This is where fellas like Bob and I disagree, but companies like Nora Rubber and I see eye to eye. Nora has one of the tightest floors on the market, and they will never accept a CaCl test. They will only allow RH testing, and it has to be a Wagner Rapid Rh test probe.

We have found the problem with testing and are eliminating it. Don't believe anything a CaCl test tells you. It means very very little.

I am under the impression "stuff" has to come out of the surface of a slab to affect the floorcovering above it. And if the emission rate is inhibited then as you commonly state that higher emisson rates will be forthcoming if you bead blast the surface.

Don't make me go back there and quote you again. lol

Your right about the revolution but still no one can explain about how at one point you guys state MVER rates in a discussion ( ie; after blasting )trying to explain issues and then again in the same paragraph or sentence deny they have anything to do with flooring failures.

Stephen you need to read what I wrote much more carefully.
I was discussing the previous poster who said he would blast the surface and install a primer. Yes blasting will open the surface and allow a higher MVER.

And while I agree it's the 'stuff' coming out of the slab that destroys the adhesives and flooring, I do not think that a low MVER is enough of an indicator that the slab is okay. This is a myth perpetuated (5) by the CaCl proponents. A slab with a low MVER can still be actively hydrating, and can be extremely volatile. When you put a moisture sensitive flooring on a slab that has high potential for changing its state, you are risking complete failure.

Ah ha! So you admit it is MVER that attacks a slab yet the F-2170 will not tell ya what that MVER is going to be. Yet, these mitigation systems still tell you "protects up to ______ in lbs/24/1000. Kinda weird doncha think?

If they denounce the CaCl tests then why are they still using the old technospeak for Cacl?

Therefore why even do any sort of test. Why not just go in and just do a mitigation test and be done with it? Blast it, seal it and forget it.

Folks, we need to listen to JD here. He is a voice of reason who understands this concept of MVER pretty well. Power troweling or hard plating a slab will lower its permeability to breathe; it has been proven in the CTL Group laboratories and is a concept the PCA has been writing about for decades. Lowered MVER is always the result. Couple this with the fact that during 99.9% of all CaCl tests performed, the surface is never ground open to 20"x20" and gassed off for 24-hrs. This is but one reason why the lower MVER scores are the result. Since ASTM F-1869-11 has now been introduced, there are even more reasons to run scared from this standard. It has become worse than a classic horror show. It is simply a culmination of 70 years of bad, bad, bad science that began in 1941 by Armstrong with no pedigree, no substantiated research to back it, and was elevated from qualitative to quantitative status in the 1960s by virtue of no quantifiable research merits. It continues to this day as simply nothing more than a surface test, that measures only 90% of the artificially extracted moisture through a non-calibrated desiccant that happens to absorb moisture, to a depth of only 1/2" and nothing past 3/4".

The moisture that comes out of the on-grade slab is meaningless. What is still hydrating within the slab at 40% depth is the ONLY meaningful issue to know. The RapidRH 4.0 is the most accurate predictor and the best indicator of what happens if the slab is capped with a floor covering or coating, and the rest of the internal vapor equilibrating within it. This is the science that is real. These are the reasons our colleagues in Europe don't have our problems with wet slabs and fast track nightmares (they also don't use .70 to .80 w/c ratios either.)

There is only one patented RH system sensor design on the planet, at this particular time, that measures small air volume at the PRECISE 40% depth that ASTM F-2170-09 calls for...with a sensor chip embedded within it...and then complies with 2170 further by providing within the test kit a NIST-traceable certificate to PROVE it is calibrated when it goes into the test hole. This is huge in a court of law, my friends. Wagner RapidRH 4.0 is that RH system. If you are going to talk compliance to ASTM F-2170-09, the in-situ RH test method that most fully complies with this standard, when performed correctly, is the Wagner RapidRH 4.0. Don't even get me started talking about slotted sleeves that allow ambient air in-and-out or leap frogging of non-calibrated reader devices; all of these will reflect lower RH scores. Additionally, there is no merit in trying to dredge up reasoning that CaCL still offers hope. It doesn't. The 1869 test method has been completely and exhaustively disarmed, through scientific laboratory research and field testing, of any credibility and authenticity in this industry. Like the Europeans did in 1987, the U.S. floor covering industry has moved on since 2002. It's time we all did our due diligence and apply the science we have learned. The CTL Group and the Portland Cement Association (PCA), both from Skokie, IL., are leading from the front with the research findings. Wagner Electronics is right there with them.

It's time to investigate the results for yourselves. I'm not bankrolling future floor failures due to a lack of knowledge and understanding. How about you?

(08-21-2011, 04:29 PM)Ernesto Wrote: Ah ha! So you admit it is MVER that attacks a slab yet the F-2170 will not tell ya what that MVER is going to be.

Therefore why even do any sort of test. Why not just go in and just do a mitigation test and be done with it? Blast it, seal it and forget it.

No, MVER is the rate of transmission. A slab can have low MVER and fail. A slab can have high MVER and never fail. It's what's INSIDE the slab that matters. The RH test will tell you what's inside the slab.

You show me a slab that has a low MVER and I'll get a very high MVER reading from it. The test is flawed and not worth the time it takes to conduct it.

Mitigation creates a barrier much different than a burned concrete cap. Mitigating a slab keeps the moisture and alkalinity from affecting the adhesive no matter how volatile the concrete is.
Thank you for chiming in David, your posts are always concise and eloquent, easy to follow and make perfect sense!

Kind of the opposite of many of my posts

I started my response to Stephen then had to cook up a grill full of steak kabobs for my family. They were delicious! Now I'm back and see I wasn't needed here at all!

You guys know I work with this issue every day, and as we speak the mayor of my little town is mad as heck with me because his new police station is being held up by slab moisture. The CaCl tests are just fine, but the flooring installer has been through a couple of failures where I came in and proved the RH was far too high for a successful floor.
The installer now uses Rapid RH probes and refuses to install the floor. I met with the construction team and concurred with the decision to hold off.
From the installer's view, he has had failures on floors that read great by CaCl, but failed. He has not had a failure on floors that have good RH numbers, or on floors I have mitigated for him. He is not willing to take that expensive gamble no matter how mad the mayor gets.

I try to spread the word that MVER is not the indicator we need for slab readiness. If you have EVER had a floor fail where the initial CaCl test was good, you need to ask yourself how it was possible and what makes the most sense to explain it. It's not that we have dozens of floors sweating during installation, it's not voodoo moisture attacking, the reason was probably inside the slab all along and we DO have the ability to see it before we begin flooring.

Posted by dlpaal - Today 03:47 PMThe moisture that comes out of the on-grade slab is meaningless. What is still hydrating within the slab at 40% depth is the ONLY meaningful issue to know<<<

If emissions makes no difference then why are you sealing the top with moisture mitigation systems?

I've read everything your speaking of dlpaal, your not telling me anything I don't already know, but ya'll cannot answer my questions concisely. Difference is that people have to prove to me what they are saying. I just don't run with the latest pack.

Now, tell me is this "science" formal science or applied science? Do you know the difference and would it matter?